Method for controlling and/or regulating the braking torque in a drive train, and control and regulating system

ABSTRACT

The aim of the invention is to regulate the braking torque in a drive train comprising an internal combustion engine ( 2 ) and a gearbox unit ( 3 ) which can be coupled to the same, using a regulatable clutch ( 5 ). To this end, the power introduced by the wheels into the drive train of the vehicle is transmitted via the regulatable clutch ( 5 ), in the overrun condition. The torque which can be transferred via the regulatable hydrodynamic clutch is controlled or regulated in such a way that the drive motor connected to the gearbox unit is operated at a rotational speed n m-soil  which is equal to or larger than the idling rotational speed n Leerlauf .

CROSS-REFERENCE TO RELATED APPLICATION

This application is related to and claims the benefit under 35 U.S.C.§119 and 35 U.S.C. §365 of International Application No.PCT/EP2002/10360, filed Sep. 16, 2002.

BACKGROUND OF THE INVENTION

The invention relates to a method for controlling and/or regulating thedrag torque in a drive train. More specifically, the invention relatesto a control and/or regulating system that is assigned to a drive trainfor controlling and/or regulating the drag torque.

Methods for regulating the drag moment in drive trains of variousdesigns are well known, and these especially include diesel-electricdrive trains, but also conventional mechanical drive trains in variousforms. In a conventional drive train with an internal-combustion engineand a mechanical drive train that comprises a gearbox unit connected tothe engine, during the drag operation mode phase, a reversal of theenergy flow occurs, i.e., power from the wheels is introduced into thevehicle, and serves the purpose of driving the drive train from thewheels to the internal-combustion engine. The document DE 43 34 210 A1discloses a control system that can be used to operate an assembly for avehicle, preferably a motor vehicle, in which at least a clutch isprovided between an internal-combustion engine and a gearbox unit. Inorder to save fuel, by using a drive assembly of this kind in tandemwith a control computer, during the drag operation mode phase, the driveengine is uncoupled from the gearbox unit and shut down. In order to endthe drag operation mode phase, it is sufficient to actuate the footthrottle with a certain deflection angle and/or a certain speed ofchange in the deflection angle. In order to prevent a knowledgeabledriver from knowingly interrupting the drag operation mode phase (andthus increasing the fuel consumption) by prematurely actuating the footthrottle, which would create an engine-braking effect for a shortperiod, DE 43 34 210 A1 proposes to continuously measure the rotationalspeed of the gearbox's outgoing shaft and the position of the controllever during the drag operation mode phase and to assign the results toa reference value stored in computer memory. A subsequent comparison ofthis value, which characterizes the position of the foot throttle, makesit possible to re-engage the above-mentioned clutch during the dragoperation mode phase only when the determined position of the footthrottle matches the actual position of the foot throttle. Thus, thefuel-saving effect is achieved by uncoupling the drive engine. However,it requires the actuation of at least one control element, and the dragoperation mode itself cannot be influenced, especially in regards to thespeed of the vehicle. When travelling downhill, this solution isespecially disadvantageous, because it does not allow one to utilize thebraking moment of the inertia of the internal-combustion engine.Therefore, this solution requires actuating additional braking equipmentto avoid undesired acceleration. Furthermore, in this design, theinternal-combustion engine is always uncoupled, irrespective of whetherthe engine braking moment can be utilized positively or negatively.

SUMMARY OF THE INVENTION

Therefore, the technical task of the present invention is to develop amethod for controlling and/or regulating the drag moment in a drivetrain with an internal-combustion engine and a gearbox unit connectedwith the engine, comprising a regulatable clutch, whose drive and outputsides can be connected, directly or indirectly through other powertransmission elements, with the gear box input and output in the dragoperation mode phase so that, irrespective of whether the engine-brakingmoment is large (in order to achieve a desirable prevention of an abruptincrease in the acceleration of the vehicle) or small, a fuel-savingdriving mode is enabled. The solution, according to the invention,should also necessitate as small an expense on control technology aspossible and should do so by using systems that are already available.

The features of the claims characterize the solution to theabove-mentioned technical task according to the invention.

The method for controlling and/or regulating the drag torque in a drivetrain that comprises an internal-combustion engine and a gearbox unitwhich can be coupled to the same, and further comprising a regulatableclutch between the gearbox unit input and the gearbox unit output, whosedrive side is connected, at least indirectly, with the gearbox unitinput, and whose output side is connected, at least indirectly, with thegearbox unit output, is characterized in that, during a drag operationmode phase, the power introduced from the wheels into the drive train ofthe vehicle is transferred by the regulatable clutch. The momenttransferred by the clutch is controlled or regulated in such a way thatthe drive engine connected to the gearbox unit is operated at arotational speed n_(M-Reference) which is equal to or greater than theidling rotational speed n_(Idle-Run). This design has the advantage thatthe fuel supply of the engine is reduced or automatically and completelyinterrupted. The reduction or complete interruption of the fuel supplydepends on whether the power introduced into the vehicle andtheoretically available for the internal-combustion engine to drive thesystem in drag (push) operation mode or pull operation mode is, indeed,sufficient to operate the internal-combustion engine at idlingrotational speed or at a higher rotational speed.

The solution provided by the present invention has the advantage of asubstantial reduction in fuel consumption as compared with theconventional arrangement in a mechanical drive train with a permanentcoupling. This advantage results from the fact that the vehicle is notdelayed by an unnecessarily high drag torque of the internal-combustionengine due to the rotational speed resulting from the transmission ofthe gearbox. Thus, a vehicle riding uphill or on level terrain behavessimilarly to how it does when idling. This method can be applied withoutany restrictions for rides over level terrain with little or noadditional acceleration of the vehicle. In accordance with a furtheradvantageous development of the method designed by this invention, thismethod can also be modified and applied to downhill rides by adjustingthe appropriate control of the transferable moment of the clutch toensure a ride with an almost constant speed v_(constant), or at least toprevent the vehicle from accelerating greatly. The rotational speed ofthe internal-combustion engine is regulated in dependence on the desiredtravel speed, while taking into consideration the transmission unitarranged between the internal-combustion engine and the wheels and theconnected transmission ratios. This solution allows one to keep aconstant speed, in a simple manner, even during the drag operation modephase and to adjust this speed to the concrete requirements, whileoptimally utilizing the available engine drag torque.

According to an especially advantageous embodiment of the invention, themethod for controlling and/or regulating the drag torque is implementedin a drive train that comprises a drive engine and a gearbox unit, whichcan be coupled to the drive train, which further comprises ahydrodynamic clutch and a bypass clutch, which can be connected inparallel, and the bypass clutch serves the purpose of the mechanicalcoupling between the primary and secondary wheels of the hydrodynamicclutch. During the drag operation mode phase, the power introduced bythe wheels into the vehicle, and especially into the drive train, istransferred by the hydrodynamic clutch. For this purpose, the bypassclutch is deactivated. Furthermore, according to the invention, themoment transmitted by the hydrodynamic clutch is controlled andregulated by changing the mass flow, and especially the filling ratio,in such a way that the drive engine connected to the input of the gearunit, and thus to the drive side of the hydrodynamic clutch, is operatedat a rotational speed equal to or greater than the idling rotationalspeed, and thus the fuel supply to the internal-combustion engine isreduced or automatically and completely disconnected. Due to thehydrodynamic power transmission, the drag torque is controlled free ofwear. The drive side of the hydrodynamic clutch is formed by the bucketwheel, which, during the transmission of the power from the drive engineto the gearbox unit output, functions as an impeller.

In this type of situation, should the moment transmitted by thehydrodynamic clutch be insufficient, the bypass clutch can be engagedand thus be operated as a bypass clutch regulated by slip control. Inthe drag operation mode, the drive power present at the wheels is thentransmitted through two power branches, where the moment actuallytransmitted can be freely set (using the hydrodynamic clutch) bychanging the filling ratio.

The method designed according to this invention can be applied to anytype of non-continuously changeable gearbox units, gear-change units,automatic gear-change units or automatic transmissions.

In detail, the method designed according to the present invention worksas follows:

During the ride, the presence of the drag operation mode is monitoredand—if identified—this mode is recorded. In the simplest case, the dragoperation mode is characterized by the non-actuation of the footthrottle and, furthermore, by a travel speed of >0 km/h. The indicatedparameters, i.e., the values that, at least indirectly, describe theposition of the foot throttle and the speed, are recorded. The nature ofthese parameters is such that, by using them, one can derive, forexample, the speed, by means of mathematical or other direct relations.

In order to also identify the drag operation mode phase during adownhill ride, and with the foot throttle being simultaneously actuated,when the drag moment introduced by the wheels in the drive train isgreater than the moment generated at the drive engine, for example, aparameter directly or indirectly characterizing the inclination of thevehicle can also be recorded, wherein the actuation of the foot throttleoccurs in a range that allows one to identify a minute available drivemoment at the internal-combustion engine, and thus is also monitored.

Furthermore, the rotational speed of the internal-combustion enginen_(Engine-Actual) is being compared with the idling rotational speedn_(Idle-Run). If the rotational speed is equal to or greater than theidling rotational speed, the engine control shuts off the fuel supply.If, due to the internal resistance of the drive train, the share of pullpower theoretically available to the internal-combustion engine is lessthan the power required for achieving the idling rotational speed, thefuel supply is only reduced. The idling rotational speed or a minutelyhigher rotational speed can be reached within the scope of the overallcontrol; however, the idling rotational speed n_(Idle-Run), present atthe internal-combustion engine, or a higher rotational speed, areentered into the system by means of regulating the correspondinglyproportional rotational speed at the input of the gearbox unit. Thistype of regulation is especially of importance if a certain speed or aspeed within a certain range is required, i.e., if it is required thatthe vehicle does not accelerate or accelerates only minutely, which isof extreme importance, for example, while riding downhill.

A parameter that at least indirectly characterizes the desired travelspeed to be maintained is monitored and recorded. The desired travelspeed can be the actual travel speed before the beginning of the dragoperation mode phase, or the actual travel speed at the beginning of thedrag operation mode phase, or a lower desired speed to be set by thedriver. In accordance with this reference value for the travel speed,and thus with the rotational speed of the wheels, theinternal-combustion engine rotational speed n_(Engine-target) (which isequal to or greater than the idling rotational speed n_(Idle-Run)) isset, taking into consideration the transmission elements between thewheels and the internal-combustion engine.

This rotational speed can be set by means of the regulatable clutch, byregulating the moment to be transmitted through this clutch, and doingso by changing one of the defining parameters, for example the contactpressure in a frictional clutch, or the filling ratio in a hydrodynamicclutch.

In automatic gearbox units with a hydrodynamic clutch and a bypassclutch, after identifying the drag operation mode phase, there are twopossibilities. The design of an automatic gearbox unit with ahydrodynamic clutch that can be completely emptied, does not require aseparate clutch. In this case, one must determine, in a second step,whether the hydrodynamic clutch, and especially the toroidal workingspace between the primary and secondary wheels, is at least partiallyfilled. If this is not the case, the filling process is initiated byactuating a device that influences the filling ratio. If thehydrodynamic clutch is filled (a minimum filling ratio must apply here),the bypass clutch is opened. The deactivation of the bypass clutch canoccur

-   -   a) simultaneously with the initiation of the filling process, or    -   b) with a time delay, however, at the latest, it should occur        upon the completion of the filling process or upon reaching a        minimum filling ratio.

After the deactivation of the bypass clutch, the power transmissionbetween the input of the gear unit and the subsequent stages or betweenthe other mechanical torque-transformation devices with fixedtransmission ratios will only occur through the hydrodynamic powerbranch. In automatic gearbox units with a transmission separationclutch, the hydrodynamic clutch can be continuously filled, which is whythe second step of verifying the filling does not need to be performedin this type of clutch, and is thus optional. In order for thetransmission of power to occur only through the hydrodynamic branch, thebypass clutch must be opened. Thus, in an automatic gear unit without atransmission separation clutch, the bypass clutch is opened in a thirdprocedural step.

In the subsequent fourth procedural step, the actual rotational speedn_(Engine-Actual) of the internal-combustion engine is compared with theidling rotational speed n_(Idle-Run), as has been described above. Ifthe rotational speed is equal to or greater than the idling rotationalspeed, the engine control shuts off the fuel supply. If the pull powershare theoretically available to the internal-combustion engine (due tothe internal resistance of the drive train) is less than the powerrequired for achieving the idling rotational speed, the fuel supply isonly reduced. The idling rotational speed or a minutely higherrotational speed can be set within the scope of the overall control;however, the idling rotational speed n_(Idle-Run) present in theinternal-combustion engine or a higher rotational speed should beentered into the system by means of regulating the correspondinglyproportional rotational speed at the input of the gearbox unit. Thistype of regulation is especially of importance if a certain speed or aspeed within a certain range is required, i.e., it is required that thevehicle does not accelerate or accelerates only minutely, which is ofextreme importance when riding downhill. This rotational speed can beset by means of the regulatable clutch, by regulating the moment to betransmitted through this clutch, and doing so by changing the fillingratio.

The method designed according to this invention is suitable forapplication in drive trains with gear units of any type—manual gearboxesor preferably automatic gear units and automatic transmissions—thatcomprise a regulatable clutch, for example, a hydrodynamic clutch.

As for the equipment, the implementation of the control and regulationfunctions requires a control and regulation system specifically assignedto the drive train. This system comprises a control device, preferably acontrol unit specifically assigned to the gearbox unit, and an enginecontrol unit specifically assigned to the internal-combustion engine.The two control units can also be integrated in one single device, andthe function can be taken over by a drive control device. The term“control device” is understood to include a control unit, monitoring andrecording equipment and regulating equipment as well as the requiredlinks—wireless, electronic, etc.—between them. The control device of thegearbox unit comprises:

-   -   at least one input for serial data transmission, or a number of        parallel inputs that are connected to a monitoring and recording        device, which records a parameter at least indirectly        characterizing the actual rotational speed of the        internal-combustion engine (n_(Engine-Actual));    -   (if the regulatable clutch is designed as a hydrodynamic clutch        with an assigned bypass clutch) a device for monitoring and        recording a parameter at least indirectly characterizing the        actuation of the bypass clutch;    -   a device for monitoring and recording a parameter at least        indirectly characterizing the filling of the hydrodynamic        component, especially a hydrodynamic clutch, and    -   a device for monitoring and recording a parameter at least        indirectly characterizing the presence of the drag operation        mode.

This data can also be provided through a communication network, forexample, a CAN bus, if available. The control unit, preferably thecontrol unit of the gearbox unit, processes this data and, following theprocedural steps, generates the regulation parameters required toregulate individual elements of the gearbox unit, especially todeactivate the bypass clutch and to fill, or more accurately, toinfluence the filling ratio of the hydrodynamic clutch, and to regulatethe regulatable clutch. The reduction of the fuel supply occursautomatically, according to the rotational speed of the drive engine, bymeans of a control device assigned to the internal-combustion engine. Asfor the concrete design of the control device, there are a number ofoptions to perform the algorithm described in the figures. Theindividual evaluation devices can be formed by separate elements, orthey can be integrated in one single evaluation device.

BRIEF DESCRIPTION OF THE DRAWINGS

The solution designed according to the invention will now be explainedin detail using the attached figures. The content of the figures is asfollows.

FIG. 1 illustrates, in schematically simplified representation, a drivesystem—in which the method according to the invention isimplemented—with an automatic gearbox comprising a hydrodynamic clutchas a regulatable clutch;

FIG. 2 illustrates, using a signal flow diagram, the underlying idea ofthe invented method when used in a drive system as shown in FIG. 1;

FIG. 3 illustrates, using a signal flow diagram, the underlying idea ofthe regulation of the rotational speed during a downhill ride for adrive system designed as shown in FIG. 1;

FIG. 4 illustrates the setting of reference positions of the footthrottle;

FIG. 5 illustrates, in schematically simplified representation, thebasic design of a control and regulation system for a drive systemimplementing The invented method;

FIG. 6 illustrates, using a signal flow diagram, the general underlyingidea of the invented method.

DETAILED DESCRIPTION

FIG. 1 illustrates, in schematically simplified representation, a drivesystem 1, in which the method according to the invention is implementedin a particularly advantageous manner. The system comprises aninternal-combustion engine 2, and a gearbox unit 3 that can bemechanically connected to it. The gearbox unit is designed as anautomatic gearbox. In this type of gearbox, the power between thegearbox unit and the drive engine can be completely interrupted duringthe gear-changing process. The gearbox unit 3 comprises an initiatingelement 4 in the form of a regulatable clutch 26 (FIG. 5)—here ahydrodynamic clutch—and a gear component 6, which is coupled to thisstarting element 4, and which can have the form of subsequently arrangedstages. The drive end of the initiating element 4—marked here with 8—isconnected with the gearbox input E—seen in the force flow direction intraction operation from the internal-combustion engine towards thedrive. The output of the subsequent stages usually forms the output A ofthe entire gearbox unit. This output is connected—through additionaltransmission means, for example, in the form of a shaft assembly and/ortorque-converting devices—with the driven wheels 9.1, 9.2 of a vehicle10. The gearbox unit 3 further comprises an engageable and disengageableclutch 11 as a bypass clutch 12, which can be engaged parallel to thehydrodynamic clutch 5. The power transmission occurs either in a firstpower branch 13, when the power is transmitted through the hydrodynamicclutch 5, or in a second power branch 14, when the power is transmittedthrough an engaged bypass clutch 12. As the system is designed, acomplete interruption of the force flow between the internal-combustionengine and the gearbox unit 3 during the gear changing requires either aseparating clutch or a complete emptying of the hydrodynamic clutch 5,especially if the bypass clutch 12 is deactivated. If a separatingclutch is provided, it can either be integrated in the gearbox unit 3or, alternatively, be arranged between the internal-combustion engine 2and the gearbox unit 3 as marked with a broken line and the referencenumber 39 in FIG. 1.

The driving power is provided by the internal-combustion engine 2. Thepower supply is controlled by an operation element 15, designed, forexample, as a foot throttle 16, which is connected with a regulator 17in the form of a power regulator of the internal-combustion engine 2.Preferably, the connection should occur through a so-calledengine-control device 18, which comprises control equipment 19 in theform of a motor control unit and which converts at least one signal—forthe driver's wish to accelerate or decelerate—into at least onecorresponding regulation signal for the regulator 17. Furthermore, acontrol device 20 is provided, preferably in the form of a gearboxcontrol unit, which comprises a control contrivance 21 in the form of agearbox control unit, and which serves the purpose—besides controllingindividual regulators that operate the regulating elements in thegearbox unit 3 representing individual gears—of controlling the powertransmission through the hydrodynamic clutch 5, especially during thedrag operation mode. While the traction operation occurs in the form ofpower transmission between the internal-combustion engine 2 and theoutput 22 in the form of the driven wheels 9.1 and 9.2, the dragoperation mode is characterized by a reversal of the energy flowdirection. Upon release of the foot throttle 16 and/or during a downhillride, the wheels 9.1 and 9.2 will drive the internal-combustion engine2. In accordance with the invention, during the drag operation mode, thepower is transmitted by the hydrodynamic clutch 5, which means that thebypass clutch 12 is opened, i.e., deactivated, and the hydrodynamicclutch 5 is controlled or regulated—with regard to its torquetransmission behavior—by changing its filling ratio in such a way that atorque of at least M_(Engine-Drag) is introduced from the output, i.e.the wheels 9.1 and 9.2, into the internal-combustion engine 2, so thatthe engine is operated at a rotational speed n₁, which is greater thanor equal to the idling rotational speed n_(Idle-Run). Furthermore, uponreaching the rotational speed n₁, the engine control device assigned tothe internal-combustion engine 2 reduces or shuts off the fuel supply.FIG. 2 illustrates this procedure in the form of a flow diagram. Duringa normal operation, immediately after starting up the vehicle 10, in afirst procedural step S1, any presence of a drag operation mode, orrather a parameter directly or indirectly characterizing the presence ofthe drag operation mode, is constantly monitored and recorded for theentire duration of the vehicle's operation. If the vehicle 10 isdetected to be in drag operation mode, which in the simplest case ischaracterized by the non-actuation or release of the foot throttle 16and a speed v>0 km/h, the system will check whether the hydrodynamicclutch 5 is filled (as shown in the signal flow diagram in FIG. 2). Ifit is not filled, the filling process is initiated. When thehydrodynamic clutch 5 is at least partly filled, the bypass clutch 12 isreleased, i.e., deactivated. The procedural step of checking the fillingof the hydrodynamic clutch 5 is required only for automatic gearboxes,which do not have a separating clutch and which realize the completeinterruption of the force flow during the gear-changing process byemptying the hydrodynamic clutch 5. This step can be left out if thecomplete interruption of the force flow between the internal-combustionengine 2 and the gearbox unit 3 is realized by means of a separatingclutch. In this process, during a drag operation mode, the bypass clutch12 is deactivated. With this type of gearbox, this occurs in theprocedural step S2, and in a third step in automatic gearboxes that haveno separating clutch and thus the possibility of completely interruptingthe power flow by emptying the hydrodynamic clutch, as shown in FIG. 2.During this third step S3, the system can also verify whether the bypassclutch is activated and, if so, deactivate it. At the latest, the powertransmission occurs upon a complete deactivation of the bypass clutch 12through a first power branch 13, i.e., through the hydrodynamic clutch 5and—seen from the internal-combustion engine to the wheels—from theactual output side 22 to the drive side 8. Moreover, depending on theavailable drag power, the fuel supply is interrupted or at least reducedin the next procedural step S4. In order to ensure a smooth operation ofthe drive system 1, the internal-combustion engine 2 must be operated atthe idling rotational speed n_(Idle-Run) or greater. The engine will usethe power transmitted through the hydrodynamic clutch 5, and willrequire enough power to allow the drive engine to operate, i.e., theinternal-combustion engine 2 at the idling rotational speedn_(Idle-Run), which will mean that the inherent internal resistance hasbeen overcome. Depending on the available power introduced by the wheels9.1 and 9.2 to overcome the resistance in the drive system, which isdesignated as P_(Drag), the torque M_(Clutch-Drag) transmitted by thehydrodynamic clutch is influenced by regulating the hydrodynamic clutch,especially its filling ratio, in such a way that enough torqueM_(Clutch-Drag) is introduced into the internal-combustion engine 2 sothat the internal-combustion engine can operate at an idling rotationalspeed n_(Idle-Run) or at a higher speed n_(Engine-Drag). The rotationalspeed n_(Engine-Drag) of the internal-combustion engine 2 equals eitherthe rotational speed at the input E of the gearbox unit 3, and thusequals the rotational speed of the drive side 8 of the hydrodynamicclutch 5 during the drag operation mode, which serves as the outputside, or is at least proportional to this rotational speed; however, wemust always take into consideration any internal friction loss oradditional interconnected transmission elements. The power P_(rec)available from the hydrodynamic clutch 5 equals the drag power P_(drag)introduced by the wheels 9.1 and 9.2 minus the power P_(D-drag) requiredto drive the remaining drive train between the clutch 5 and the wheels9.1 and 9.2. The influencing of the transmittable torque (and due to theequality of torques between the output side and the drive side 8 of thehydrodynamic clutch 5 with the same power presentP_(clutch)=P_(drag)−P_(D-Drag)) a conversion of the rotational speedoccurs, allowing one to set a rotational speed n_(Engine-Drag-Actual) ³n_(Idle-Run) using the interdependence of the transmission devicesbetween the internal-combustion engine 2 and the gear unit 3. Thus, thetarget rotational speed n_(Engine-Target) of the internal-combustionengine 2 is equal to or greater than the idling rotational speedn_(Idle-Run), and is thus a function of the torque M_(Clutch-Drag)transmittable by the clutch. So, the target rotational speedn_(Engine-Target) can either only be set by the regulation system orfurther regulated, in which case (as shown in the signal flow diagram inFIG. 2) the target rotational speed n_(Engine-Target) of theinternal-combustion engine 2 is continuously compared with the actualset rotational speed n_(Engine-Actual). The reduction or completedisconnection of the fuel supply depends on whether the powerP_(Engine-Drag-Theoretical) introduced into the vehicle andtheoretically available to the internal-combustion engine in the pull ordrag operation modes is really sufficient to operate theinternal-combustion engine at the idling rotational speed n_(Idle-Run)or at a higher rotational speed. The fuel supply is automaticallyreduced or completely disconnected by the engine control device uponreaching the desired rotational speed.

In this design, the procedure shown in FIG. 2 applies to ride situationsin the pull operation mode that are characterized by a ride speed of >0km/h and the non-actuation of the foot throttle 16, when theacceleration can be negative or positive. However, the drag operationmode also occurs during a downhill ride, which is not necessarilycharacterized by the non-actuation of the foot throttle 16. In otherwords, this drag operation mode occurs when the power P_(Drag)introduced into the vehicle is greater than the power P_(E-Actual) setby the power regulator of the internal-combustion engine 2 as the powerto be achieved. This is especially the case with steep downhill slopes.As for the presence of the drag operation mode, various parameters canbe applied. One of the safe parameters is the actuation of the footthrottle. However, for the case of a downhill ride where the footthrottle 16 is still being actuated, there must be one more parametercharacterizing the drag operation mode to be monitored and recorded, forexample, the drag torque introduced by the wheels. In this case, thevehicle is in the drag operation mode if the introduced torque isgreater than the torque generated by the drive engine. In such asituation, especially when the foot throttle is still being actuated,the torque introduced by the wheels 9.1 and 9.2 would be equidirectionalwith the torque generated by the internal-combustion engine 2, and wouldhave to be added. The procedural step of verifying whether thehydrodynamic clutch 5 is filled or not, is relevant only for automaticgearboxes without a special separating clutch. In automatic gearboxeswith a separating clutch, the hydrodynamic clutch 5 can always befilled, which is why this procedural step can be left out. However, inaccordance with an advantageous embodiment of the invention, this stepis still included for safety reasons.

The rotational speed of the drive engine in the form of theinternal-combustion engine 2 can be set or, in an advantageousembodiment of the invention, further regulated. Thus, as shown in thesignal flow diagram in FIG. 2, in a fifth procedural step, the actualrotational speed of the engine n_(E-Actual) is compared with the idlingrotational speed n_(Idling) or another, higher rotational speed, whichis also designated as n_(E-Target). If the rotational speed n_(E-Actual)of the internal-combustion engine is lower than the idling rotationalspeed n_(Idling) or another higher rotational speed n_(E-Target), thehydrodynamic clutch 5 is regulated—with regard to its torquetransmission capacity—so that a rotational speed is set (by changing thefilling ratio ΔFG) on the drive side 8, which is now acting as theoutput side, that is equal or proportional to the idling rotationalspeed n_(Idling) or another higher rotational speed n_(E-Target). Thishigher rotational speed n_(E-Target) can be permanently pre-set, or canbe freely regulated within a range depending on the size of theavailable drag power.

As for the possibility of regulating the torque transmitted by thehydrodynamic clutch 5, there are several options; the preferred one is asimple pressure regulation. This regulation occurs when an externalcircuit assigned to the hydrodynamic clutch closes. This circuitconnects an inlet with an outlet of the working space by generatingand/or exerting pressure on a medium. During the operation of thehydrodynamic clutch 5, a portion of the medium present in the workingspace is conducted, through a closed circuit, between at least oneoutlet from the toroidal working space between the impeller and theturbine wheel, and at least one inlet to the toroidal working space,while the inlet is connected with a medium storage container, which ispressure sealed from the ambient area. A parameter characterizing thepressure to be exerted on the medium present in the medium storagecontainer is generated, and the regulator is actuated. The filling oremptying of the hydrodynamic clutch continues until a pressureequilibrium is reached between the medium in the medium storagecontainer and the medium rotating in the closed circuit. Another option,which works especially well for hydrodynamic clutches without suchclosed systems, consists in regulating the filling ratio by controllingthe hydrodynamic clutch's inlet and/or outlet pressures. However, theconcrete selection of the possibility to change the filling ratiodepends on the concrete design and the available supply systems. Aconcrete selection and adaptation should be done at the discretion ofthe expert.

With regard to the equipment, the drive system 1 is assigned a controland/or regulation system 23 (FIG. 5), which comprises a control device18 assigned to the internal-combustion engine and a control device 20assigned to the gear unit. The control device comprises a control unit19 in the form of an engine control device, and serves the purpose ofcontrolling a power regulator in the form of a regulating device 17designed to control the fuel supply. The control device 20 in the formof a gearbox control contrivance comprises a gearbox control unit 21,which—besides controlling individual regulators that actuate individualregulating elements of the gear unit 3—also serves to control the powertransmission in the hydrodynamic clutch 5. The term “control device”always includes monitoring and recording equipment and regulatingequipment, as well as the links between the output(s) of the monitoringand recording equipment and the regulating equipment. A control deviceusually includes a control unit in the form of a microcomputer with acorresponding memory capacity, or a combination of a microcomputer withadditional function components. The control device processes a number ofincoming signals and converts them into a set of regulation signals. Thecontrol device 21 comprises—depending on whether it uses serial orparallel data transmission—at least one input 24 (FIG. 5), which islinked to a device 25 that monitors and records at least one parametercharacterizing, at least indirectly, the presence or absence of a dragoperation mode. Furthermore, the control device 21 is fed a signal thatcontains at least one parameter characterizing, at least indirectly, theactual filling ratio, which can occur through the same input 24, orthrough an additional input 25. For this purpose, this input is linkedto a device that monitors and records the filling situation in thehydrodynamic clutch. This device is designated with the reference number26. The rotational speed n_(E-Actual) of the drive engine 2 is usuallyrecorded by the data acquisition device 28, which is assigned to theinternal-combustion engine 2, and which can be connected to the controldevice 21 either directly through a direct link with an output 27, orindirectly, through a data communication network, for example, a CANbus. Depending on whether a reduction of the fuel consumption byreducing the fuel supply or a complete disconnection of the fuel supplyis desired, it is useful to also determine the amount of theoreticallyavailable drag power P_(Engine-Drag-Theoretical), or at least aparameter characterizing, at least indirectly, this amount. This processrequires the corresponding data recording equipment 29.1 to 29.n thatdetermines or computes the power introduced by the wheels into thevehicle during the drag operation mode phase, and makes it possible todetermine the drag power theoretically available to the engine. Theseparameters are fed into the system through an input 30. If serial datatransmission is used, the control device 21 has only one input. Withinthe control unit 21, an evaluation unit 31 checks whether the vehiclefinds itself in the drag operation mode or not. If the drag operationmode is positively determined, then—depending on the gearbox system(with or without a separating clutch)—the filling ratio is checked,i.e., the signal incoming at the input 25 is evaluated. This can occurin the same evaluation unit 31, or in another evaluation unit 32.Depending on the filling ratio of the hydrodynamic clutch 5, theactivation of the bypass clutch is then checked. For this purpose, asignal incoming at the input 32 (which characterizes the actuation ornon-actuation of the bypass clutch) is evaluated. If the bypass clutchis activated, a regulating signal to deactivate it is sent from anoutput 32. However, the activation of the bypass clutch does not need tobe specially checked, and a separate signal does not need to beretrieved through the input 31. It can be derived from the current gearstatus, which must be stored in the control device 21. Furthermore, thecontrol device comprises an additional evaluation unit 35, which can becontained in one construction unit together with the evaluation units 31and 32, or its function can be assumed by one single evaluation unit.This evaluation device compares the current rotational speed of theengine n_(engine-actual) with the idling rotational speed. As an option,if this rotational speed is exceeded, the system compares the drag powertheoretically available to the internal-combustion engineP_(Engine-drag-theoretical) with the idling rotational speedP_(drag-idle-run). Should the power introduced by the wheels into thevehicle be less than the power required for idle run, the engine controldevice only reduces the fuel supply and regulates theinternal-combustion engine in such a way that the remaining powerrequired for the idle run is generated by the engine, i.e., the torquegenerated by the engine M_(engine-generated) and the drag torqueintroduced into the internal-combustion engine M_(drag) are addedtogether. On the other hand, when the power introduced by the wheelsinto the vehicle is greater than the power required for an idle run, thefuel supply can be completely shut off. In both cases, a power regulator17 of the internal-combustion engine is actuated by the engine powercontrol unit through an output 36, which is connected either directly tothe power regulator 17 or to the control device 19 of the control deviceof the internal-combustion engine. This link can be mechanical orwireless. However, in both cases, the torque transmitted by thehydrodynamic clutch M_(drag-clutch) is regulated in such a way that therotational speed at the drive side 8 in the traction operation mode, andat the input E acting as the output side side in the drag operationmode, is equal to or greater than the idling rotational speed of theinternal-combustion engine 2 n_(idling), or is proportional to therotational speed of the internal-combustion engine 2 so that therotational speed of the internal-combustion engine 2 is always equal toor greater than the idling rotational speed, while taking intoconsideration all interconnected transmission elements. For thispurpose, a regulating parameter Y is released at the output 37 in orderto change the filling ratio, for example, by means of pressure, or bychanging the position of a valve. The output 37 is linked to a devicethat influences the filling ratio 38.

The solution designed according to the invention serves the purpose ofreducing the fuel consumption during the drag operation mode byregulating the drag torque in the drive train with a gearbox in such away that the drive engine is operated at a minimum idling rotationalspeed. The concrete implementation and equipment is not limited to thedesign as shown in FIG. 3. Other modifications are possible. Forexample, the individual devices could be integrated in a single controldevice, or the function of this control device could be assumed by thedrive control or another control device. As for the link between theindividual data acquisition equipment and the control devices, there arealso a number of options available. The individual parameters could beavailable to each of the control devices in a network, for example, in aCAN bus. Other options, for example, a direct mechanical link, are alsoconceivable. These design choices depend on the concrete conditions ofthe invention's expected use.

FIG. 4 illustrates a possible range division of the foot throttle. Inorder to avoid too abrupt a transition between the drag operation mode(with a drag torque between 0% and 100%) and the status of riding with apositive drive torque (the foot throttle sets a positive torque, i.e.,allows fuel supply to the internal-combustion engine), the function ofthe foot throttle must be extended. The schematically simplifiedrepresentation shows three positions. Position B represents a zero dragtorque and, simultaneously, an engine torque set to zero. The positionat rest represents the maximum possible drag torque present with theengine rotational speed n_(Engine-Actual) ³ N_(Idle-Run), and theposition “Max” represents the maximum settable engine torque. Thisallows one to achieve a continuous, smooth transition from the maximumdrag torque with a closed bypass clutch to the minimum drag torquearising when the invented procedure is applied at a maximum reducedrotational speed of the engine, to drag torque=0/engine torque=0 in theposition B and to maximum engine torque in the position “Max.” Upon theshift from the drag operation mode into an operation with a positiveengine torque, i.e., upon changing the foot throttle position from therange between its rest position and B into the range between B and“Max,” the bypass clutch is closed again. This can occur in dependenceon the rotational speed of the engine.

In another aspect of the invention, the drag torque transmitted by thehydrodynamic clutch is controlled, or rather regulated, in such a waythat the vehicle does not achieve any positive accelerationa_(ppositive). For this purpose, a parameter at least indirectlycharacterizing the acceleration ‘a’ is continuously determined and, independence on the desired riding speed to be maintained, the rotationalspeed in the drive train—and thus the rotational speed of the wheels tobe driven—while taking into consideration the necessity to operate theinternal-combustion engine 2 at a minimum idling rotational speedn_(idling)—is influenced in such a way that the riding speed defined bymeans of the rotational speed of the wheels does not exceed a presetlimit. This speed can be the current riding speed, or the actual ridingspeed at the moment, when the drag operation mode started, or anotherspeed defined by the driver, which, however, should lie within the rangebetween the two aforementioned speeds. For this purpose, a rotationalspeed n_(engine-target) for the internal-combustion engine 2 is derivedfrom the desired target riding velocity v_(target), while taking intoconsideration the transmission elements arranged between the wheels andthe internal-combustion engine 2. This rotational speed is proportionalto the rotational speed of the wheels, which allows one to achieve aconstant riding velocity v_(constant). The changing of the filling ratioFR of the hydrodynamic clutch 5 occurs so that, depending on theavailable power, enough torque M is transmitted to cause a rotationalspeed of n_(Engine-actual)=n_(Engine-target). In this case, setting therotational speed of the internal-combustion engine 2 to a rotationalspeed n_(Engine-target) equal to or greater than the idling rotationalspeed n_(idle-run) is integrated into maintaining a constant ridingvelocity v_(constant).

FIG. 6 illustrates, using a signal flow diagram, the underlying idea ofthe invented method for a gearbox unit with a regulatable clutch 26between a gearbox input E and a gearbox output A, wherein the drive sideof the regulatable clutch 26 is connected, at least in a transmittedway, i.e., directly or indirectly, by additional transmission elements,with the gearbox input, and the output side is connected with thegearbox output A, directly or indirectly, by additional transmissionelements. Here, too, during the riding operation the presence of thedrag operation mode is being verified. The drag operation mode ischaracterized by a riding operation with a velocity V>0 km/h and thenon-actuation of the foot throttle. The acceleration of the vehicle canbe positive or negative. After the drag operation mode is detected, therotational speed of the drive engine is determined and is then comparedwith a desired rotational speed n_(Engine-Target), which is onlyminutely greater than the idling rotational speed. If the idlingrotational speed or the desired rotational speed n_(Engine-Target) hasalready been reached, the engine control automatically shuts off thefuel supply. This occurs in a third step that follows the second step.Otherwise, the theoretical drag torque introduced by the wheels into theengine through the drive train is compared with the actual power P_(M)generated by the drive engine. If the theoretically available drag poweris sufficient to operate the internal-combustion engine at the idlingrotational speed, the regulatable clutch lets through only enough dragtorque M_(drag) to the internal-combustion engine as is necessary toreach the idling rotational speed n_(engine-idle-run). Depending on thedesign of the regulatable clutch, this means a change in the regulationparameter Y, which is sent to the regulator. In a hydrodynamic clutch,this is the filling ratio ΔFR, whereas, for example, in a frictionclutch, the regulation parameter represents the force F_(A) applied tothe clutch's friction elements. This occurs until the idling rotationalspeed n_(engine-idle-run), is reached, or until the desired target speedn_(Engine-Target) equals the idling rotational speed or a minutelyhigher rotational speed.

LIST OF REFERENCE NUMBERS

-   1 Drive system-   2 Internal-combustion engine-   3 Gearbox unit-   4 Starting element-   5 Hydrodynamic clutch-   6 Gearbox part-   7 Subsequent stage-   8 Drive side-   9.1, 9.2 Wheels-   10 Vehicle-   11 Regulatable Clutch-   12 Bypass clutch-   13 First power branch-   14 Second power branch-   15 Operation element-   16 Foot throttle-   17 Regulator-   18 Control contrivance-   19 Control device-   20 Control contrivance-   21 Control device-   22 Drive side-   23 Control and/or regulation system-   24 Input-   25 Device for detecting at least one parameter at least indirectly    characterizing the drag operation mode-   25 Input-   26 Regulatable clutch-   26 Device for detecting the filling ratio, i.e., the filling status    of the hydrodynamic clutch-   27 Input-   28 Device for detecting the rotational speed of the    internal-combustion engine-   29.1, 29.n Devices for detecting the parameters for the description    of the drag power P_(engine-drag) theoretically available to the    internal-combustion engine-   30 Input-   31 Evaluation unit-   32 Evaluation unit-   33 Input-   34 Output-   35 Evaluation device-   36 Output-   37 Output-   38 Device for influencing the filling ratio of the hydrodynamic    clutch-   39 Separating clutch-   E Gearbox clutch-   A Gearbox output-   P_(drag) The power introduced into the vehicle by the wheels-   P_(rec) Power receivable by the hydrodynamic clutch-   M_(drag) Drag torque of the clutch-   M_(engine-drag) Drag torque introduced into the internal-combustion    engine-   n_(clutch-drag) Rotational speed of the hydrodynamic clutch-   n_(Engine-actual) Actual rotational speed of the internal-combustion    engine in the pull operation mode-   n_(Idling) Idling rotational speed-   n_(Engine-target) Target rotational speed of the internal-combustion    engine in the pull operation mode

1. A method for controlling and/or regulating drag torque in a drivetrain comprising an internal-combustion drive engine, and a gearbox unithaving an input and and output, the gearbox unit coupled to the engine,and a regulatable clutch between the gearbox input and output, the drivetrain drive side coupled at least indirectly to the gearbox input and,as seen in the direction of power transmission during tractionoperation, the drive train output side coupled, at least indirectly, tothe gearbox output; said method comprising: during drag operation mode,transmitting by the regulatable clutch power introduced by wheels of thedrive train into the drive train; resulting torque transmitted by theregulatable clutch being controlled and regulated such that the enginecoupled to the gearbox is operated at a rotational speedn_(engine-target), that is equal to or greater than the engine idlingspeed n_(idling); the regulatable clutch being a hydrodynamic clutchwith an assigned bypass clutch for a mechanical bypass between the driveside and output side of the hydrodynamic clutch, the hydrodynamic clutchand the bypass clutch being engageable in parallel operation; andcontrolling the torque transmitted by the hydrodynamic clutch bychanging the filling ratio thereof.
 2. The method according to claim 1wherein, while moving downhill in the drag operation mode, the driveengine is operated at a rotational speed n_(engine-target), which isgreater than the idling rotational speed, whereinn_(engine-target)—while taking into consideration transmission elementsin the drive train-causes a certain travel velocity v_(target) of thevehicle.
 3. The method according to claim 2, wherein the travel velocityv_(target) is achieved by regulating the rotational speed of the driveengine.
 4. The method according to claim 1, wherein the rotational speedn_(engine-target) of the drive engine is regulated.
 5. The methodaccording to claim 1, wherein when drag power introduced into thevehicle and theoretically available to the internal-combustion engine isless than the power required to drag the internal-combustion engine withthe idling rotational speed n_(idling), the fuel supply is reduced. 6.The method according to claim 1, wherein the drag operation mode can bedescribed by one of the following parameters: velocity v>0 km/h, and afoot throttle or any other operation element used by the driver isreleased.
 7. The method according to claim 1, wherein the drag operationmode can be described by one of the following parameters: velocity v>0km/h, and a parameter that describes, at least indirectly, thelongitudinal inclination while moving downhill.
 8. The method accordingto claim claim 1 wherein, in the drag operation mode, the bypass clutchis deactivated.
 9. The method according to claim 1, wherein, if the dragtorque is greater than the torque theoretically transmittable by thehydrodynamic clutch when fully filled, the bypass clutch is closed andis operated in the slip mode, wherein drag power introduced into thedrive train is transmitted in a first power branch through the bypassclutch and in a second power branch through the hydrodynamic clutch. 10.The method according to claim 1 wherein: the hydrodynamic clutch can becompletely emptied; in the drag operation mode the filling status of thehydrodynamic clutch is determined, and if it is not filled or is filledbelow a minimum filling level, the filling process is initiated; thebypass clutch is deactivated at a point between the time the presence ofthe drag operation mode is determined and the completion of the fillingof the hydrodynamic clutch.
 11. A control and regulation system forsetting drag torque in a drive train, comprising: an internal combustionengine; a gearbox unit coupled to the engine and having an input and anoutput; a regulatable clutch in the form of a hydrodynamic clutchbetween the gearbox input and output, the drive train drive side coupledat least indirectly to the gearbox unit and, as seen in the direction ofpower transmission during traction operation, the drive train outputside coupled, at least indirectly, to the gearbox output; means forcontrolling and regulating torque transmitted by the hydrodynamic clutchsuch that the engine is operated at a rotational speed n_(engine-target)that is equal to or greater than the engine idling speedn_(engine-idling), said means for controlling comprising a means forchanging the filling ratio of said hydrodynamic clutch; a mechanicalbypass clutch assigned to said hydrodynamic clutch to thereby provide amechanical bypass between a drive side and an output side of thehydrodynamic clutch; said bypass clutch and said hydrodynamic clutchbeing engageable in parallel operation.
 12. The control and regulationsystem according to claim 11, wherein the means for controlling isformed by a gearbox control unit.
 13. The control and regulation systemaccording to claim 11, comprising: an additional engine control deviceassigned to the internal-combustion engine comprising at least one inputand one output; the control device input is linked to an output of thecontrol device or to a device for detecting a parameter that leastindirectly characterizes the current rotational speed of theinternal-combustion engine; the output of the engine control device islinked to a regulator changing the fuel supply.
 14. The control andregulation system according to claim 13, wherein the engine controldevice comprises a microcomputer, which—when the internal-combustionengine reaches the idling rotational speed n_(idling), generates aregulation parameter for the regulator to shut off the fuel supply. 15.The control and regulation system according to claim 13, wherein theengine control device comprises a microcomputer which, upon theinternal-combustion engine reaching the desired rotational speedn_(engine-actual)=n_(engine-target)>n_(idling), generates a regulationparameter for the engine control device to change the fuel supply. 16.The control and regulation system according to claim 11, wherein a linkbetween the means for controlling and data acquisition devices iswireless.
 17. The control and regulation system according to claim 11,wherein the means for controlling and an engine control device arelinked by a data communication network.
 18. The control and regulationsystem according to claim 11, comprising: a device for the detection ofa parameter at least indirectly characterizing the actuation of anoperation element, the device being linked with an input of the meansfor controlling.
 19. The control and regulation system according toclaim 11, comprising: one or a number of devices for the detection ofparameters that characterize the theoretical drag power P_(engine-drag)available to the internal-combustion engine and that are connected withthe input of the means for controlling.
 20. The control and regulationsystem according to claim 11, comprising: inputs connected with a devicefor the detection of the filling status of the hydrodynamic clutch, anda device for the detection of a parameter at least indirectlycharacterizing the actuation status of the bypass clutch; an interfaceconnected to the means for controlling and to a device for thedeactivation of the bypass clutch.
 21. A drive train, comprising anoperation element actuated by the driver in order to change the ridingstatus; and a control and regulation system according to claim
 11. 22.The drive-train according to claim 11, wherein the gearbox unit isdesigned as a manual gear-changing box.
 23. The drive-train according toclaim 11, wherein the gearbox unit is designed as an automaticgear-changing box.
 24. The drive-train according to claim 11, whereinthe gearbox unit is designed as an automatic transmission.